The invention relates generally to a photocopy machine for exposing and developing diazotype copy materials wherein a liquid developer in metered quantities is applied to the exposed copy material to produce dry to the touch developed copies.
More specifically, the invention relates to a drive means for selectively operating the exposure and applicator rollers in a first mode in which the rollers are positively driven in one direction during normal machine operation when copies are being made, and a second mode in which the rollers are freely rotatable in either direction to facilitate removal of a sheet jam at either of the rollers and servicing of the machine.
In some instances a copy sheet may, instead of existing from the developer section of the machine in the normal manner, tend to cling to the applicator roller and become wrapped around the roller under blades or other developer dispenser and wiper means normally provided for applying and metering the liquid developer on the applicator roller surface. Also, a copy sheet or an original to be copied may, instead of exiting from the exposure section of the machine in the normal manner, tend to cling to the exposure roller. Although an occurrence of this kind is rare, when it does occur it is difficult to remove the wrapped-up copy sheet or original without extensive time and effort. Therefore, it is desirable and an object of the present invention to provide a means to facilitate removal of a sheet jam at either the exposure or the applicator roller.
One arrangement to aid in the removal of a copy sheet jam at the applicator roller only is shown in U.S. Pat. No. 3,702,096 assigned to the same assignee as the present invention. This patent discloses a copy apparatus employing an over-running slip clutch provided in a drive train between the applicator roller and a motor for driving the roller. The motor is selectively energized to operate in either a forward or a reverse direction, and the clutch normally drives the roller in one direction when the motor is energized in an operating mode. When the motor is energized for reversing the direction of driving torque applied to the roller, the roller may be rotated in either direction for relieving a copy sheet jam. When the motor is operating in the reverse direction in the prior art patent, the roller may be manually rotated in either direction as a result of the reverse drive and the action of the over-running clutch.
The prior art device requires special and costly circuitry for reversing the drive of the motor and roller, and insuring that the blades which provide the contact pressures for copying are not brought to bear on the applicator roller, and to insure that the developer fluid is not further applied to the roller. All of the foregoing must be accomplished prior to clearing any sheet jam. This special circuitry adds substantially to the cost of the apparatus.
Still further, the prior art does not provide for operating the apparatus directly to the free wheeling mode when the applicator roller is being driven in a forward direction or when the machine is shut off. Rather, the apparatus can be operated to the free wheeling mode only when the forward drive of the applicator roller is arrested and the motor is energized to operate in a reverse direction, after the machine has shut off. Unlike the present invention which provides for free wheeling of both the exposure and the applicator roller to facilitate servicing of the machine and removal of a sheet jam at either of the rollers, the prior device provides for free wheeling of the applicator roller only.